The present invention relates to the exhaust gas emitted from a turbomachine, and more particularly to a system for reducing the harmful constituents within the exhaust gas before recirculating the exhaust gas back into the turbomachine.
There is a growing concern over the long-term effects of Nitrous Oxide (hereinafter NOx) and Carbon Dioxide (hereinafter “CO2”) and Sulfur emissions on the environment. The allowable levels of NOx and CO2 that may be emitted by a turbomachine, such as a gas turbine, are heavily regulated. Operators of turbomachines desire methods of reducing the levels of NOx and CO2 emitted.
Exhaust gas recirculation (EGR) generally involves recirculating a portion of the emitted exhaust through an inlet portion of the turbomachine where it is mixed with the incoming airflow prior to combustion. This process facilitates the removal and sequestration of the emitted NOx and concentrated CO2 levels, thereby reducing the net emission levels.
There are a few problems with the currently known EGR systems. Impurities and moisture within the exhaust gas prevent utilizing a simple re-circulating loop to reduce the CO2 and NOx reduction. Turbine fouling, corrosion, and accelerated wear of internal turbomachine components would result from introducing the exhaust gas directly to the turbomachine inlet portion. As a result, the diverted exhaust gas should be treated prior to blending with the inlet air. Significant amounts of condensable vapors exist in the exhaust gas stream. These vapors usually contain a variety of constituents such as water vapor, acids, aldehydes, hydrocarbons, sulfur, and chlorine compounds. Left untreated, these constituents will accelerate corrosion and the fouling of the internal components, if allowed to enter the inlet of a gas turbine.
For the foregoing reasons, there is a need for system for treating the re-circulated exhaust gas stream to minimize the impact of harmful constituents within the exhaust gas stream on turbomachine components.